DIY LED array

[PaulS]

DIY LED would be a good topic for a future meeting.

[gconcepcion]

This is one of the arrays I have. I would love to add some white light LED's to it. Unfortunately I know nothing about electronics.

http://www.groworganic.com/item_GP834_S ... ro_Ba.html

Interesting light, though I can't seem to find much in the product literature in terms of specifications...

What size tank are you going to be using this on? 29g? What degree optics are you using? The problem with led's is coverage. The tighter the optics, (better par in deeper tanks) the closer the led's have to be to avoid spotlighting. I think you'll more than happy with the par readings, depending on the depth of the tank (and optic choice) you might find it to be too much. This was the case with my led fixture, I run them at no more than 600ma.

The array will go on a 29 gallon (18" depth). I got the 60 degree optics, which with LED spacing of ~2inches should give me roughly the equivalent of a 150 watt HQI (or so i'm told by some of the reef lighting gurus) at the substrate level.

With only 12 LED's if I position them 2" apart from eachother, i'll only have coverage in the center of the tank... so in lieu of that, i'm going to have to space them a little bit further, and experiment with distance from water surface and/or trying different optics if i'm not happy with the light spread from the 60 degree lenses.

Did you build a dimmer box? that's something I haven't even thought about yet but probably should before it becomes the next bottleneck since the heatsink was ordered lastnight. I hope to start wiring this weekend or early next week.

[John G]

DIY LED would be a good topic for a future meeting.

I agree.

[Ltrepeter2000]

Lets let this experiment play out before we make it a meeting topic. I would think we need to know the specifics of what works before we dedicate that kind of time for all the members.

Rob

[SCMurphy]

• Plant Grow Light Efficiency - greater than 90%
  Targeted Plant Growth & Health Peak Spectrum - greater than 95%
  Operating Temperature - less than 15 degrees above ambient temperatures
  Power Consumption - 6-9 Watts
  Power Supply - International 120/240
  Electrical Hazard - No
  Fire Hazard - No
  Glass Breakage Hazard - No
  Peripheral Support Needed - No
  Ultra-Violet Light Emissions - No
  White-light Pollution - No
  Environmental Impact - Minimal
  Time to Full Output After Power Interruption - Instant Full Power
  Configuration Considerations for deployment - No
  Fixture Mounting Considerations - User option, LED Grow Master grow lights are easily mounted either vertically or horizontally
  Bar Weight - .75lbs 21" x 2.5" x 1" (533.40mm x 63.50mm x .38mm)
  SunMount - 1.5 lbs 28" x 6" x 1"
  Power Adaptor - .75 lbs 3" x 3" x 7"
  Operating Life - 11 years estimated, with 0% plant light degradation at 24/7 operation

[ingg]

I've seen a few aesome DIY LED's built.

Not for the faint of heart.

Between understand the heat sinks for CREE's in a tight array, having the capability of actually making the pjysical soldering connections so the heat sink works, and the ciruitry involved, it was quite an amazing project - much of which was either beyond my tools, or my understanding of circuitry.

[gconcepcion]

The heatsink got here today. I ordered the 5.375" wide model 22" long from heatsinkusa.com it was $45 + $5 cut fee + $15 shipping, for a total of $60. So far i've spend $145 + $60 = $205 on this little project. I was hoping to keep the whole thing under $200, but it looks like with wires + any other circuitry stuff I will need (or anything else i've forgotten) it will be more in the $220-$240 ballpark.

I also didn't anticipate having to build my own PWM LED dimmer... not that much in cost (~$10 worth of resisters, capacitors, timing chips etc) just a little more effort than I was anticipating.

As far as the heatsink goes, I ordered one wide enough so I can add an additional row down the center, and more columns in between the current columns if I don't think i'm getting good enough light spread...

Next step is to drill a bunch of tap holes so that after I apply the thermal adhesive to the LED's, I can secure them in place with screws.

After drilling the holes, I need to polish the bottom surface with sandpaper to eliminate any bumps or grooves so that the heat transfer from LED to heatsink will be as efficient as possible.

Now I have to figure out if i'll be able to drill the heatsink at home with my hand drill or if i'll have to beg a friend (or the machine shop on campus) to let me use a drill press

[JSnyder]

Next step is to drill a bunch of tap holes so that after I apply the thermal adhesive to the LED's, I can secure them in place with screws.

If your going through all of the hassle of drilling and tapping the holes, skip the thermal epoxy and go with standard thermal paste (arctic silver 5) The epoxy is meant as a permanent mounting solution and thermal conductor in one, (no need to drill and tap holes) and transfers heat to the heat sink well, but not as good as the pressure from the screws and a standard thermal paste.
Also keep in mind if anything happens to one of the cree's in your array, your most likely going to have to chisel it off, possibly damaging the H/S.
If your dead set on using the epoxy, The right amount of pressure, and the right length of time are important for it to set properly. The best way to accomplish this is to cut a single square of egg crate (light diffuser) and place it over the led's lens, this will protect the led from getting crushed. place a phone book over the egg crate square and led and let it set for 1 hr.

After drilling the holes, I need to polish the bottom surface with sandpaper to eliminate any bumps or grooves so that the heat transfer from LED to heat sink will be as efficient as possible.

People make way too big a deal out of this, I understand the need to lapp a H/S for a computer processor, as your dissipating 100w or more of power over a small area. For a bunch of 3w leds spread over that large surface the factory finish should be fine. The thermal compound (or epoxy) will fill any imperfections. If you should want to spend your time doing it, use 2000 grit paper and then flitz polish. it will end up with a mirror finish.

Now I have to figure out if i'll be able to drill the heatsink at home with my hand drill or if i'll have to beg a friend (or the machine shop on campus) to let me use a drill press

It's more consistent and faster to do it with a drill press. Hand drill is just as easy, if taking a bit more time. Center punch your holes so the bit doesn't "walk." Keep the drill as vertical and even as possible, to avoid crooked holes. Use even pressure and speed.

[gconcepcion]

If your going through all of the hassle of drilling and tapping the holes, skip the thermal epoxy and go with standard thermal paste (arctic silver 5) The epoxy is meant as a permanent mounting solution and thermal conductor in one, (no need to drill and tap holes) and transfers heat to the heat sink well, but not as good as the pressure from the screws and a standard thermal paste.
Also keep in mind if anything happens to one of the cree's in your array, your most likely going to have to chisel it off, possibly damaging the H/S.
If your dead set on using the epoxy, The right amount of pressure, and the right length of time are important for it to set properly. The best way to accomplish this is to cut a single square of egg crate (light diffuser) and place it over the led's lens, this will protect the led from getting crushed. place a phone book over the egg crate square and led and let it set for 1 hr.

I didn't realize that the ceramic based arctic alumina thermal epoxy that they sent with it was intended to be permanent. I'm definitely set on being able to reconfigure at a later date if necessary, so I think I will forgo the Arctic Alumina in favor of the several tubes of Arctic Silver 5 I have stockpiled in my computer parts drawer.

Thanks for the heads up.

People make way too big a deal out of this, I understand the need to lapp a H/S for a computer processor, as your dissipating 100w or more of power over a small area. For a bunch of 3w leds spread over that large surface the factory finish should be fine. The thermal compound (or epoxy) will fill any imperfections. If you should want to spend your time doing it, use 2000 grit paper and then flitz polish. it will end up with a mirror finish.

I realize this, but I would hate to do something half-assed
Plus I like shiny!

Do you think active cooling is necessary? I have a couple of spare computer fans that I was going to mount to the top of the heatsink if it gets too hot, but the heatsink may be large enough that passive cooling is sufficient. Any thoughts?

It's more consistent and faster to do it with a drill press. Hand drill is just as easy, if taking a bit more time. Center punch your holes so the bit doesn't "walk." Keep the drill as vertical and even as possible, to avoid crooked holes. Use even pressure and speed.

I definitely would prefer a drill press, as I have 66 holes to drill on the bottom side (extra holes for multiple configuration options), but I will drill one or two holes this weekend with my hand drill and try to figure out just how irritated / frustrated I will be after another 64 or so.

[Conagher]

I recently read an article on dealing with LED heat...

http://www.designnews.com/article/45128 ... id=2716411

This might be a bit redundant and basic information at this point, but I thought I would share.